Walker’s campaign on Thursday announced it had produced ads attacking both Falk and Barrett, but would not say where the ads were running.

Ken Goldstein of Kantar Media/Campaign Media Analysis Group said Friday that the Barrett ad is the only one running on stations across Wisconsin. Barrett spokesman Phil Walzak says that shows Walker views Barrett as his likely opponent in the June 5 election.

Walker’s campaign spokeswoman Ciara Matthews declined to comment.

The Democratic primary is May 8. In addition to Barrett and Falk, Secretary of State Doug La Follette and state Sen. Kathleen Vinehout are also running.